Road signposts are subject to being struck by a vehicle and as a result be broken off at the base of the signpost. At higher speeds, or for signs having large upper mass, there is little opportunity to prevent breakage, plastic deformation or other loss of the sign. Solid signposts break off regardless of the speed of impact. However, at lower vehicle/sign impact speeds it is desirable to have a sign post which gives way and then springs back. Municipalities spend significant money and personnel resources to repair the many broken road signs.
In one approach to this problem, municipalities have generally provided a small base plate secured to the ground and having with a cup and transverse post-pinch bolt. A crew typically cuts off the broken bottom of the typically metal post and reinserts the cut end back into the cup, the repaired sign being slightly shorter but often not too badly damaged. While the material cost is low, the need for the attendance of maintenance personnel causes the cost to be high.
It is known to provide spring-loaded signpost bases to reduce the incidence of sign damage and obviate the need for a repair crew to attend at every impact occurrence. Many of these prior art bases utilize extension tension springs which are subject to breakage, particularly at the hooked ends. Example of such devices using an extension spring are U.S. Pat. Nos. 4,106,879 and 4,270,873 issued to Diedershagen and Laehy et al. respectively. These devices and others like U.S. Pat. No. 5,703,577 to Carter use above-ground components which are very exposed and subject to post-impact damage by the offending vehicle. Others do not automatically center on their base and return to a standing position such as in U.S. Pat. No. 3,838,661 issued to Hedley, Jr.
In U.S. Pat. No. 5,199,814, Clark et al. describe a short plastic post which is used for delineation of vehicle paths comprising facing truncated conical load bearing cells. One cell has its conical base secured to the ground and one cell has it conical base secured to an upstanding plastic post. The two cells truncated tips bear against each other with their axes normally aligned. The post extends upwardly from the conical base and contains a compression spring which tensions two cables which pass through the two cells. The tensioned cables pull the tips of the two cells to urge the post to remain vertically aligned. Like several of the other prior art designs, the heavy coil spring and related apparatus are located above the ground.
The Clark apparatus is a unitary assembly, providing the self-righting apparatus and post as one. The small conical cell tips are not conducive to supporting a large of tall signpost, or a retrofit post. The short post and apparatus are vulnerable to damage upon impact as the apparatus, spring and plastic post are above ground at the level of impact by the offending vehicle. Damage of the post requires replacement of substantially all of the apparatus. Further, the Clark apparatus is not amenable to retrofit of conventional metal road signposts.
Large numbers of metal signposts are in use by municipalities. The current preference of municipalities is to merely cut off and replace the existing metal posts, not substitute an all-new signposts. There is therefore a demonstrated need for a simple and robust self-righting apparatus which, most preferably is one which will adapt to the existing signposts typically in use.